Remote control system



June 6, 1944. G. w. BAUGHMAN 'E1-A1. 2,350,668-

REMQTE CONTROL SYSTEM l I Y .Filed Aug. 21, 1942 4'sheetsjsheet 1 June 6, 1944- G. w. BAUGHMAN ET A1. v 2,350,668

REMOTE CONTROL SYSTEM Filed Aug. 21, 1942 4 sheets-sheet 2 ZI @16H Y 11:. F j?? Uffieelz'n@ [/fu' @i :im f l- -E-/V 7. ai

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'Salapage Um? I y 'af Szalion-i THE/f1 Arma/WK n 4 sheets-sheet 4 v Patented June 6, 1944 REMOTE CONTROL SYSTEM George W. Baughman, Swissvale, and Norman F. Agnew, Penn Township, Allegheny County, Pa., assignors to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Penn- Sylvania Application August 21, 1942, Serial No. 455,577

13 Claims.

Our invention relates to remote control systems, and more particularly, to the communication or line circuits for such systems.

Our invention is particularly adapted for, though in no manner limited to, centralized traffic control systems for railroads, in which a train dispatchers oce or other suitable point of control is connected with a plurality of eld stations by line wires, over which impulse codes of signals are transmitted for controlling selected track switches and railway signals at the stations, and for indicating, at the control oflice, the condition of the controlled switches and signals, and for also indicating the positions of trains in the controlled territory.

Our invention may advantageously be applied, for example, to the centralized traic control system of the time code type, such as is disclosed in Letters Patent of the United States No. 2,229,249, granted January 21, 1941, to L. V. Lewis, for Remote control systems.

In Letters Patent of the United States No. 2,208,446, granted July 16, 1940, to G. W. Baugh'- man, for Remote control apparatus, means are disclosed for providing additional communication channels for telephone communication or for code signaling, or both, over the series line circuit of the system of the above-mentioned Lewis patent, and for utilizing these additional channels to provide a multiplex C. T. C. system in which a plurality of sets of coding apparatus employ the same line wires without interference.v

In accordance with this arrangement, when the number of stations or the length of the line is greater than can be well handled by the system as shown in the Lewis patent, the line is divided into sections by means of electrical filters or the like at one or more points, each section providing a battery line circuit for the control of the usual number of way stations, and the code signals transmitted between the control oflice and the stations included in the remote sections are relayed over the intervening sections by the use of two non-interfering one way carrier current channels, employing alternating currents of. different frequencies.

In our prior application, Serial No. 326,440, led March 28, 1940, now Patent No. 2,303,875, issued December 1, 1942, for Remote control systems, we have disclosed improvements upon the time code system above referred to, employing a central battery bridged line circuit, which has the advantage over the series line circuit as used, for example, in the system of this Baughman patent, that the station line relays and code transmitting contacts are bridged across the line wires so that the line wires do not require to be sectionalized at any way station. In other words, our prior application discloses a remote control system of the central battery type, in which communication is eiected in two directions between the oliice and stations over line wires which are maintained continuous from end to end, as is required, for example, when the line is simplexed to provide a ground lreturn telegraph channel. This arrangement greatly facilitates the non-interfering use, by the C. T. C. system, of line wires already equipped to provide a plurality of channels for telephone or telegraph communication or for other purposes, as described more fully in our prior application.

The present invention relates to improvements upon the system of this prior application, comprising the adaptation of that system to multipleX operation along the lines of the above-mentioned Baughman patent. In accordance with our invention, one of the plurality of non-interfering communication channels which two line wires afford providesa central battery bridged line circuit for one set of C. T. C. apparatus comprising the oice and station coding units of the Lewis patent, while one or more additional sets of similar apparatus each having its own line circuitare arranged to be governed from the same central oice by remote control, each additional 4set employing two one-way channels including the same line wires, over which alternating currents of different frequencies modulated in accordance with the codes are transmitted. Line units of a novel type are interposed between the Oliice coding unit andthe battery end of the line circuit to which the station coding units are connected, at each end of the alternating current line, for effecting the transmission of the alternating current codes and for other purposes incidental to the proper operation of the system, as will now be pointed out.

In our central battery bridged line system, the transmission of indication codes from the stations to the oflice is effected by periodically connecting the line wires together at the transmitting station through a low-pass lter so as to vary the current delivered by the line battery in accordance with the code. These codes of current variations are received at the ofce by a polar line relay connected to the line through a transformer, and thereby rendered responsive to the variations. This line relay is of the magnetic stick type, arranged to be held in its last operated position when deenergized, and is so controlled by timing relays included in the office coding unit that it is automatically restored to its normal position after a time interval if it is accidentally reversed, and the relay is in that man ner maintained in its normal position when no signals are being transmitted over the line.

A feature of the present invention is the provision of means for similarly governing a line relay of this type, without the provision of corresponding timing relays, when the relay is located at a point remote from the office, at which no coding unit is available.

Another feature of our system asdisclosed in our prior application relates to provisions for preventing interference when two or more transmitters initiate their codes at the same time. These provisions include the use of current of a normal polarity for control codes, and of a reverse polarity for indication codes. The line polarity is reversed by the action of the ofce coder in response to the first impulse of an indication code," and the' station transmitter is thereby conditioned to complete its code. The oflice transmitter takes precedence if it happens toV start at the same time as a station', .while if two or more stations start at the same time, butV one remains in control of the line dependent upon the relative superiority of their respective codes. The system as disclosed herein operates similarly, and a feature of the present invention resides in the provisions for vreversing the polarity of the remote lline circuit for the transmissionof an indication code, and for restoring it to 'normal upon the receiptrof a complete code at Vthe control ofice; Y

A further feature of our invention, dependent upon the foregoing, resides in the provisions for reinitiating a station transmitter if its indication code is not received complete at the control office even' though the code is transmitted over a oneway' channel the condition of which is not observableat the/sending station.

Other objects, purposes and features of our inventi'on willbe pointed out as the description proceeds.

Two forms of apparatus embodying our invention will now be described, and the novel features thereof will then be Vpointed out in claims.

Referring to the accompanying drawings, Figs. 1A and 1B illustrate the cnice equipment, and Figs. 2Aand 2B the eld equipment for a multiplex"C. T. C. system embodying our invention.

More particularly, Fig. 1A shows in diagrammatic form the omce apparatus employed for the direct control of a group of stations located at spaced points adjacent the line wires Yl'and ZI each equipped as shown in Fig. 2A. Figs. 1B and 2B show the apparatus located respectively at the 'office and at the control end of a remote line, as arranged for the remote control of a second group of stations located at spaced points adjacent the line wires Y2 and Z2, each of which stations is also equipped as shown in Fig. 2A. This remote control apparatus of Figs. 1B and 2B is adapted to employ the saine line wires Y! and Zi as those usedY for direct control and additional sets of the remote control apparatus may be superimposed upon these line wires and also upon the line wires Yi and Z2 as required, without interference.

Referring to Fig. 1A, the apparatus enclosed within the dot-and-dash line and bearing the legend Office coding unit No. 1 comprises a portion of the oli'ce coding unit-of Fig. 1 of the Lewis Patent No. 2,229,249, modified in accordance with our invention and corresponding genpanel containing the levers and lamps required erally to the portion marked Oice in Fig. 1 of our prior application hereinbefore referred to. This coding unit is interposed in the usual manner in the connections between the line battery 8) and the line wires Yl-ZI to which the stations controlled by this office coding unit are connected. It will be understood that the remainder of this coding unit, not shown herein, and likewise the ofce storage units which it controls, `of which one is to be provided for each for the control of a station, are arranged as described in the Lewis patent. A portion of one of these storage units is shown at the right in Fig. 1A. Y

In Fig. 1B a portion of a coding unit is shown, bearing the legend Office coding unit No. 2, which is identical with the No. 1 unit in respect to its internal connections, but which is arranged to control a second group of Vstations located along a remote line circuit, by means lof connections-to an Oflice line unit, comprising a group of four relays, which in turn, is connected to the line wires Yl'and Zi through a carrier current unit containing a suitable oscillator and amplifier, and designated C. C. unit No. l.

The interposed line and C. C. units serve to transform the control codes of interrupted direct current produced by the coding unit No. 2 into modulated alternating current of frequency jl in the line YI-ZI, and to receive modulated alternating current of a different frequency f2 from the line and to transform it into codes of battery current variations to govern the line relay GR. of the coding unit.

As insurance against an interruption of service, a reserve C. C. unit No. 2, similar to the No. 1 unit, is arranged to be interposed in place of No. l by the operationr of a changeover relay ICH, in response to the closing of a manually operable key K I.

- Fig. 2A shows a portion of the station coding unit of Fig. 6 of the above-mentioned Lewis patent, but modified in accordance with our invention and corresponding generally to the portion marked C. T. C. station in Fig. 1 of our prior application above referred to. It will be underf stood that the remainder of the station coding unit, not shown herein, and likewise the station storage unit or units which it controls, function as described in the Lewis patent, and that one such coding unit is to be located at each controlled station.4 The line terminals Y and Z of the coding unitV at each station controlled by oiiice coding unit No. 1 are to be connected across line wires Y! and Zi, while those of the coding unit ateach station controlled by additional ofce coding units such as No. 2 are to be connected across the line Wires of the corresponding remote line circuit.

Fig. 2B shows the apparatus located at the control or battery end of each such remote line circuit, the line wires of the remote line shown herein being designated Y2 and Z2. This apparatus is interposed between these line Wires and another pair extending toward the ofce, such as YI and ZI, and its purpose is to transform the modulated alternating current of frequency fl received from the office into control codes of interrupted direct current in line Y2-Z2, and to transform the indication codes of battery current variations received from that line into modulated alternating current of frequency f2 in line Yl-ZI. The two lines shown in Fig. 2B may be different sections of the same through telephone line, isolated with respect to the coded currents by a band-pass filter VF or otherwise. The apparatus of Fig. 2B includes a Remote line unit comprising a, group of ve relays, and a carrier control unit designated C. C. unit No. 3 struci turally identical with the C. C. units at the office V'any one of the frequencies used in the system.

i A reserve carrier current unit, heredesignated No. 4, is arranged to be interposed in place of No. 3 by the operation of a changeover relay 2CH. This relay, moreover, is arranged to be remotely controlled from the oice by transmitting a code to the last station, designated No. 35, on the first section of the line. Thus the operator at the office, by positioning a manually operable key such as K2, Fig. 1A, is enabled to transmit a code over any sectionto replace the C. C. unit which governsl the transmission of codes over the next succeeding section of the through line. The particular carrier current units in service at any time are indicated at the ofiice by the lighting of correspondingly numbered lamps CC shown in Figs. 1A and 1B. those for the units at the ofiice being controlled directly by relay ICI-I. and those for the units at the remote location being governed by indication codes transmitted by station No. in accordance with the position of relay ZCI-I. Y

It is also to be understood that the line wires may also be used for the operation of a vtelephone call selector system, arrangedV either as shown in our prior application above referred to or in other Ways, such for example as shown in our application, Serial No. 401,092, filed July 5,

1941, now Patent No. 2,332,191, issued October 19 1943, for Remote control systems.y

A feature of our invention, as will be apparent from the foregoing, is the constructionof a system of the character described from interchange able units of a relatively few types and in the provision of arrangements for insuring continuity of service, a factor of importance in View of the large amount of apparatus that may be involved, and in view of the use of existing line Wires which may extend over relatively long distances.

Similar reference characters refer to similar parts in each of the several views.

The relays shown herein which correspond with relays of the Lewis patent are designated by the same reference characters as employed in the patent, the oflice relays being distinguished by the prex 0 and those of the remote line unit by the prefix I, Where corresponding relays are used in the oce and inthe field. In the patent, all of the code system relays are of the same general type, but some of the relays shown herein are of other types. For example, the line relays R and IR are of the stick polar type, each being adapted to hold its contacts in the last operated position when the relay is deenergized. These relays may be, for example, of the type shown in Letters Patent of the United States No. 2,140,604, granted December 20, 1938, to C. S. Snavely. The

station line relay R of Fig. 1B, and likewise relays PR, NR and DCR of the oflice line unit of Fig. 1B and relay lCR of the remote line unit of Fig. 2B are of the biased polar type, such for example, as shown in'Letters Patent of theUnited States No. 2,283,270, granted May 19, 1942, to R. M. Laurenson, each of these relays being iden tiiied by a horizontal arrow to indicate that it is responsive only to current iiowing in the corresponding direction.

It is to be understood that each biased or stick polar relay shown herein responds to close'its left-hand contacts when the positive terminal B of a suitable source of current is connectedl to its winding at the left, with the negative or common return terminal C of the same source conr` nected to its windingat the right, and that when these connections are interchanged the relay is operated to its right-hand position, the latter position being the `one to which the biased relays move their contacts when they become deener` gized. v Wires Il and I8 connected to the normal and reverse contacts of relay 0R in Figs. 1A and 1B correspond to the Wires leading from the ofce coding unit to the front and back points, respectively, of contact b of relay 0R of Fig. 1 of the Lewis Patent No. 2,229,249, While wires Ila and Ia in Fig. 2A correspond with those leading from the station coding unit to contact b of the station line relay R of the patent. l

Considering first the direct control system'v of Figs. 1A and 1B, the normally closed line circuit may be traced from the line battery through the primary of transformer d, back contacts b and d of the transmitter relay UT and of the pole changer relay PC through-a low pass lter LF to the line WiresYI and ZI, and thence in multiple, to the terminals Y and Z of thecoding unit at each station of the group controlledby` oice coding unit No. 1, Where a branch is completed as shown in Fig. 2A through the coils of a similar filter LF, back contacts y' and 7c of the master relay M and the winding of the line relay R, each station line relay being normally energized as shown. The condensers associated with the station filterV LF are normally disconnected from the line, thereby materially increasing the impedance to voice frequencies, of the connections across the line at each station, which is 4of obvious advantage since there may be a large number of such connections bridged across the same telephone line. This arrangement has the further advantage of protecting -these condensers against lightning. When relay M picks up, however, the left-hand condenser of the station lter LF is connected across terminals Y and Z at its front contact h, and the right-hand conf v denser at its front contact j, and the filter functions in the usual` manner to render the transmitted code inaudible.

With the systemv in its normal at rest condition, relay 6R` is connected to the line circuit through transformer 40, and is thereby rendered responsive to a change in line current of a'suitable amount. irrespective of its actual magnitude, and it is to be understood that contact b of relay BR is operated to the right upon an increase in line current, and to the left, as shown, upon a decrease in line current. When relay M of Fig. 2A is picked up, the closing of contact b of relay T connects the line terminals Y and Z together through filter LF to increase the line current to operate contact b of relay 0R to the right, and

the line current decreases to its normal value to restore the contact of relay UR to its left-hand position when contact b of relay T opens.

Although relay UR is normally deenergzed with its contact b held in its last operated position, its contact b normally occupies the lefthand position, corresponding to the normally en'- ergized'position of the station line relay R, for the following reason: Assume relay UR to become n reversed as a result of a momentary accidental cross between line wires YI--ZLfor example; its contact b connects terminal B of the local source of current to 'Wire I8, causing the timing relays ULI, UL2, ULP to pick upv in order, andthen relays ULB and ULBP pick up, as explained in the Lewis patent. Relay ULI becomes deenergized again, upon the opening of back contact a of relay UL2, and if relay UR remains reversed, relays ULI, ULP, ULB and ULBP then release one at a time in order, each upon completiorrofA its respective release period, relay UL2 being held energized over its contact a. When relay ULBP releases, a restoring circuit is closed from terminal B over the contacts g of relays ULBP, ULZ and ULI through the lower winding of relay UR to the other terminal C of the local source of current, thereby restoring relay UR to normal, as shown.

The reversal of relay UR has the further effect of completing a circuit from terminal B over wire I8, back contact 7' ofvrelay UM, Yback Contact h of relay UL2 or front contact h of relay ULI, back contact f of relay ULBP through the pole changer relay PC to terminal C, and relay PC picks up to complete its stick circuit at its contact a when relay ULBP picks up. Contacts b and d of relay PC reverse the polarity of the current in line YI-ZI vreleasing the line relays R at each station controlled thereoVer. By reference to Fig. 2A it will be seen that each relay R upon releasing connects terminal B to wire IUa, to cause operations of the station timing relays substantiallyin unison with the corresponding oilce timing relays as above described,

opening the pick-up circuit .for .the station master relay M at contact b of relay LI or L2 t0 prevent any station from initiating a code at this time.

At the oice, relay PC is released to restore the line polarity to normal when relay ULBP releases to restore relay UR to normal. layPC picked up, the closing of its Contact e energized a slow-acting repeater relay PCP, which relay picks up shortly thereafter and releases again shortly after relay PC releases. The operations of pole-changer contactsb and d of relay PC necessarily causes some variation in the line current through transformer 4U, but the effect of this is nullied by a shunt closed momentarily across the secondary terminals of transformer 4U and the upper winding of relay UR at contacts c ofv relays PC and PCP each time relay PC picks up or releases. Furthermore, when relay PC picksup upon the reversal of relay UR, a local circuit is closed momentarily from terminal B over contacts f and a of relays PC and PCP and the middle winding of relay UR to terminal C to maintain relay UR reversed, and when relay PC release, a second local circuit is closed momentarily over contacts f and b of relays PC and PCP and the lower winding of relay UR to maintain relay UR normal.

When relay UR is restored to normal as above described, relay ULI becomes energized over wire II and front contact ,f of relay UL2, reenergizing relays ULP, ULB and ULBP, and then relays UL2,

When re- ULP, ULB and ULBP release, conditioning the apparatus to receive a code, and finally, relay ULI is released by the opening of front contact b of relay ULBP to condition the apparatus to transmit a code. in response to the release of relay PC, the station timing relays are similarly operated.

It will be seen therefore, that although rely UR f is arranged to remain deenergized' in either position to which it is operated on the successive steps of a code, it is always restored to normal if it remains reversed for a time interval materially longer than that required for the normal operation of the system, and .that an accidental operation of that relay which leaves it in an abnormal position merely suspends the operation vof the system for but a relatively short period which in practice is in no way detrimental. v

The transmission of a control code by the apparatus of Fig. 1A will now be briefly explained, starting with the apparatus in its normal condition, as shown.

The starting relay IST corresponds to any one of the starting relays identified by a code number such as relay 234 in the Lewis patent, and when relay IST is picked up in response to the operation of the corresponding push button as described in the patent, a circuit is closed over back contacts b of relays ULI and 0 L2 to pick up relay STP, completing a circuit from terminal B at wire I1, contact m of relay UM, contacts a of relays STP and ULB through relay UM to terminal C. Relay UM picks up and at its contact 7c, shunts the upper primary winding of transformer 6U, rendering relay UR non-responsive to the operation of the tranmitting contacts b and d of relay UT in the line circuit, and prepares a circuit at its contact h to enable relay UR to be controlled locally by the operation of contact f of relay UT.` Relay UM also opens its contact y' in the circuit for relay PC to prevent the cperation of that relay, and by closing its contact e, energizes relay UT which then transmits a code of line open and line closed steps as described in the Lewis patent, the line relay R at ea ch station operating in unison with relay UR. A. control code is therefore transmitted by the office coder and received at the selected station in the manner described in the patent.

The transmission of an indication code by the apparatus of Fig. 2A will now be explained, assuming terminals Y-Z to be connected across line YI-ZI.

It will be understood that a change in condition of a station device having indications to transmit picks up the start relay ST, and if the line relayV R is steadily energized so thatvrelays LI and L2 are both released, contact c of relay ST completes a circuit from terminal B over back contacts b of relays SS, L2 and LI, contacts a of relays CO and LB, contact c of relay IU, contact d of relay E, through relay M to terminal C.

Relay M picks up to initiate the code by closing a'shunt across terminals Y-Z over its front contact j and back contact d of relay LBP, thereby reversing the ofce line relay EER and releasing the station line relay R. The front contacts h and :i of relay M lconnect the condensers of the station lilter LF across terminals Y-Z as already described, and front Contact e of relay M completes the circuit for the transmitter relay T, which then picks up to shunt terminals Y-Z over contacts b of relays T and E, while contacts y' and lc of relay M reverse the connections of When the station relays R pick up relay R to terminals Y and Z to render that relay responsive only to line current of reverse polarity, ..Relays R and R initiate the operation ofitheir respective timing relays as already de-V scribed, relay PC picking up to reverse the line polarity, thereby releasing relays R at all other stations at which relay M is released, these relays remaining released for the duration of the code to lock out their respectivestations. Relay T is rendered eiective to transmit the indication code by the opening of back contact d of relay LBP upon the initial energization of that relay, and then relay T operates its contact b repeatedly in the usual manner to transmit the code, relay R at the transmittingy station responding to the current of reverse polarity in the line, being released each time relay T picks up and energized each time relay T releases, and relay llR is operated in unison with relay R in response to the current variations impressed on the' line by the operation of contact b of relay T. The coding units therefore function in the usual manner and the indication code is transmitted by the station and received at the office as described in the patent. As explained therein, each indication code has sixteen steps, the last step comprising the return of the line circuit to normal, a relay IB at the transmitting station and a similar relay 0-I 5 at the oiiice being picked up momentarily on this step. ln the patent, all line relays assume their normal positions at the beginning of this step, but in the present case this is true of relay (3R and of relay R at the transmitting station only.

At the office, relay -lB opens its contacts d Iand e, opening the circuit over the upper Winding of relay GR to hold relayR normal, and releasing relay PC, which then releases relay PCP, thereby restoring the line polarity to normal as already described. At the` transmitting station, contact d of relay IS disconnects the right-hand contact of relay R from Wire Ia and connects it to Wire Ha, to prevent further operation of the coding unit by relay R, and contact c of relay I6 opens the circuit for relay M, releasing relay M to restore the connections of relay R to normal. The remaining operations of restoring the system to normal are eiected in the usual manner as described in the patent. Y

Code interference is` prevented as follows: First, a code cannot be initiated until the line relays have been restored to normal to release? relays L2, and relays LBP and LI have alsoV released, as already described. Second,the direction of transmission is determined in accordance with the character of the iirst impulse, which is long in each control code and short in each indication code.V Relay E is responsive to the long first stepof a control code, and in the event the oice and a station start at the same time, the line is held open by the oilice transmitter until after the timing relay LI of Fig. 2A is-released, relay l being picked up on this step,rar'1d a circuit is closed from terminal B' at front contact a'of relay LBP, back contact c of a relay SP, front contact d of relay l, back contact g of relay Ll, iront contact f of relay LBP through relay E to terminal C. Relay E picks up and its contact d opensv the circuit for relayM, which then re-y leases, completing a stick circuit for relay E and conditioning the stationunit to receive thecon-` trolV code, and the indication code is stored by Y relay fST to be transmitted subsequently as de- 'code by any station is delayed until each other tion to receive the next code.

effective to release the line relay Rat any station more remoteirom the oirlce, which has been conditioned to respond to current of reverse polarity by having its relay M picked up.A When two or more stations start to transmit indication codes at the same time, they may continue in operation as long as the code elements of theirrespective codes are alike, but when a difference occurs one or another is locked out by means o an additional pick-up circuit provided for the station relay E. In this case relays R and TYWill be out of step, that is, when relayT releases to remove the line shunt, relay R remains released due to the shuntA maintained by relay T at another. station, completing a circuit from terminal B to Wire i3d, back contact g of a relay CR,

back contact d of relay T, front contact a of relay M, front contact f of relay LBP vthrough relay E to terminal C. Relay E will pick up, opening its contact cl in the circuit for relay M, and then relay M will release, restoring the connections of relay R to normal. Relay R is thereby rendered non-responsive to the line current of reverse polarity and remains released untilthe indication code transmitted by the other station is completed, releasing its timing relays and consequently releasing relay E by the opening of contact f of relay LBP, as Well as releasing the other coding relays, as occurs under similar conditions in the system as described in the patent. Itfollows therefore that a plurality of indication codes stored by diferent stations at the same time are transmitted one at a time in order ina definite order of code superiority, as explainedmore fully` in our prior application, Se-

rial No. 326,440.

, The apparatus of Fig. 2A includes an additional feature by which undue delay in transmission oicodes from the inferior stations is avoided. In transmitting an indication code from any station, a selector relayS is picked up in response to the transmission of the corresponding code call for that station, and at the end of the code, relay SS picks up over a circuit from terminal B at contact arof relay LBP, front contact b of relay I 6, back contact g of relay E, front contact e of relay S, through relay SS to terminal C. Relay SS therefore picks up at the end of the code transmitted by the same station, and is held energized over a stick circuit extending to termi,

nal B'at iront contact g of relay LBP. As already mentioned, the release of relay LBP during the clearing out operation at the end of a code conditions the apparatus at the corresponding sta-l The opening of front contact b of each relay LBP, due to the releaseof relay LBP following the release of relay Lpattlie end or" the code, deenergizes the associated relayLl, and release of relay LI Vat any station having its relay ST picked up and its relay SS released initiates the transmission of a code by that. station. The relay SS at the'station which has just completed its code becomes .de-

energized upon the release of relay LBP, provided Consequently, when there are a plurality of indcationcodesstored, the transmission oi a second station has had a chance to transmit one code, and the maximum delay inthe transmission of any code is measured by the time required to transmit one code from each station.

The operation of the remotely controlled C. 'I'. C. system comprising Figs. 1B and 2B will now be explained, assuming that a plurality of station units of Fig. 2A similar to the one just described are connected to the line Y2-Z2.

The office line unit of Fig. 1B, which is identical with that of Fig. 1A already described, is connected to a dummy line circuit including the oppositely connected biased polar relays PR and NR of the oflce line unit. This circuit may be traced from terminal B of the local source of current through the upper primary winding of transformer 150, back contacts b of relays T and PCresistor 23 relay NR, back contacts d of relays PC and 6T, the lower primary winding oftransformer Ill) lthrough relay PR to the other terminal C 'of the same source. Relay PR is normally energized and serves as a direct repeater of relay BT to transmit control codes, while relay NC is normally held in its released position and is picked up only when its connections are reversed by relay PC as occurs when an indication code is being received.

In the carrier control unit No. 1 the oscillator OSC is normally supplied with energy at its lefthand terminals from a local alternating current source indicated by the terminals BX and CX, over back contact h of relay ICH, and constantly delivers current of frequency fl at its right-hand terminals, which are connected through filter FI over back contacts b and c of relay ICI-I to line YI--ZI, but this current of frequency f I is normallyshunted over back contacts f and g of relay ICH and contact b of relay PR, and is supplied to the line only when relay PR is released, that is, when relay 0T is picked up on the oddnumbered steps of a code.

. The currentof frequency ,fI thus is modulated by the operation of contact b of relay PR in accordance with the code, and this modulated current is :supplied over line YI-ZI and back contacts b and c of relay 2CH, Figi, 2B, through the lter FI of C. C. unit No. 3, and itis then amplified' and demodulated by a suitable amplifier as indicated by the device AMP, energized from the local alternating current terminals BX and CXas shown, and is supplied over back contacts d and Ve 'of relay 2CH to the normally deenergized biased polar relay ICR of the remote line unit; f

The remote line circuit is normally energized from the line battery 83a over the primary of transformer 40a, contact b of relay ICR, contacts b and d of the pole changer relay IPC through a'low pass lterLF connected to the line-Y2-Z2.

The line relay IR of the remote line unit of Fig. 2B is connected to the line YZ-ZZ through transformer 4ta, and controls the pole changer relay IPC and its repeater IPCP and in turn is controlled by these relays in a manner generally similar to that already described in'connection Lwith relay R. vRelay IPCP however has an additional energizing circuit extending to terminal B at the front contact a vof relay ICR, so that relay IPCP is energized on each odd-numbered step, and remains picked up for the duration of each control code. Relay IPCP holds relay- IR energized in its normal position,v as shown, by the energization 'of the lower windyassesses'` ing of relay IR over the restoring circuit including front contact b of Yrelay IPCP. Relay IPC has a pick-up circuit extending from terminal B at the right-hand contacts a of relays ICR and IR which is thus held open by relay IR, and relay IPC remains released for the duration of a control code, and the normally energized slow acting relay L remains energized over back contact e of relayIPC.

Since the connections from battery 80a to the lineare similar to those for battery 80 except that a contact b of relay ICR, which is a direct repeater of the office transmitter relay 0T, replaces' the contacts of the latter relay, it will be apparent that control codes will be delivered to line Y2'-Z2 by office coding unit No. 2 similar to those delivered to line YI-ZI by office coding unit No. 1 as already described, these codes being received by the coding units of Fig. 2A which are connected to line Y2-Z2 in a manner which will be readily understood without further description.

The line relay IR serves to receive the indication codes comprising battery current variations in line YZ-ZZ and to retransmit them as modulated alternating current of frequency f2 over line YI-ZI and its operation will now be described.

In the carriercontrol unit No. 3, the oscillator OSC is arranged to constantly deliver current of frequency f2 at its right-hand terminals, which are connected through filter F2 over back contacts b and c of relay ZCH to line YI-ZI, but this current of frequency ,f2 is normally shunted over back contacts f and g of relay 2CH and contact b of relay IR, and is supplied to the line only when relay IR is reversed. Each on period of Vthe alternating current indication code delivered by relay IR therefore corresponds to an increase in the current supplied to line Y2-Z2, dueto the closing of Contact b 0f a station transmitter relay Tto transmit an odd-numbered step of an indication code. The current of frequency f2 thus modulated by the operation of Contact b of relay IR in accordance with the code is sup-- plied over line YI-ZI and back contacts b and c of relayV ICH, Fig. 1B, through the filter F2 of C. C. unit No. 1, and it is then amplified and demodulated by amplier AMP and is supplied over contacts d and e ofA relay ICH to the normally deenergized biased polar relay UCR of the ofce line unit. When relay T picks up, therefore, the current in line Y2-Z2 is increased, relay IR is operated to the right and current of frequency f2 is supplied to line YI-ZI to energize relay UCR, which relay closes its contact b to shunt resistor 2) to cause an increase in current through transformer 4U to reverse relay 0R. Relay 0R is therefore a direct repeater .of relay I-R. 'Since relay IR is of the stick polar type, it remains to be shown how this relay is arranged to be normally self restoring.

If relay AIR becomesreversed as a result of a momentary accidental cross between line Wires Y2-Z2, for example, its Contact b removes the shunt from the line channel of frequency f2 causing relay GCR 4to pick up, thereby reversing relay IlR of Fig.1B. Relay IR also closes its cony tact a causing relays IPC and IPCP to pick up shunting contact b of relay ICR to prevent'theopening of line Y2-Z2 in response to a control code impulse of frequency fI, relay L also opening its contact c in the shunt across line Y2Z2 which includes the left-hand contact b of relay ICR and resistor E. This shunt normally provides a discharge path for the distributed capacity of the line as is desirable when the line is in cable, and corresponds to the similar ones associated with the relays 6T and described in the Baughman Letters Patent of the United States No 2,208,446, hereinbefore referred to.

At the oice, the reversal of relay R of Fig. 1B

causes the timing relays and relays PC and PCP` contact a of relay NR completes the circuit for aV slow release relay TA which picks up and at its contact b opens the shunt across the oscillator terminals normally closed over contact b of relayy PR. Relay NR now replaces relay PR in preventing the delivery of current of frequency fl to line YI-ZI. The'ofce timing relays, with the eX- ception of relay SL22, now release in sequence, relay ULBP, the last to release, restoring relay DR and deenergizing relay PC as already described.

Relay PC, upon releasing, restores relay NR to its normal position as shown, and relay NR by opening contact b allows current of frequency fl to be delivered to the line to energize relay ICR. Contact a of relay ICR is therefore operated to the left, releasing relay IPC but holding relay IPCP energized, and these relays cause the energization of the lower winding of relay IR over their respective contacts f and b to operate relay IR to normal and to hold it energized in that position.

The restoration of relay NR to normal by relay PC opens the circuit for relay TA which releases after an appropriate time interval to terminato the impulse of current of frequency fl, whereupon relay ICR releases, and in turn releases relay IPCP.l

The release of relay IPC reenergizes relay L and restores the polarity of the current in line Y2-Z2 to normal, reenergizing the station line relays, and finally the timing relays LI-LBP become energized and release in the usual manner to condition the system to send and receive codes.

The transmission of an indication code by the apparatus of Fig, 2A will now be explained, assuming terminals Y-Z to be connected across a line Y2--Z2 having its connections to the contro-l oice eifected over line YI-ZI by means of the two one-way carrier channels provided bythe apparatus of Figs. 1B and 2B.

Y Assuming the apparatus to be in its normal condition as shown, when the start relay ST of Fig. 2A is operated, relays'M and T pickup as already described, shunting line Y2--Z2 to cause relay IR of Fig. 2B to reverse, thereby supplying currentof frequency f2 to line Yi-ZI to energize relay `(JCR and consequently increasing the current through transformer 4l] to cause relay 0R of Fig. 1B to reverse. the timing relays and in addition the relays NR and TA become energized, and in Fig. 2B, relays IPC and IPCP become energized, deenergizing relay Lyas already described. Since relay ICR is Relays PC, PCP and porarilydiscontinue the operation of the station not energized at. this, time, relay IPC remains energized over its stick circuit regardless of the operation of relay IR and reverses the polarity of :the current supplied to line Y2-Z2 to allow relay T at the transmitting station to deliver its code to operate relay IR. Current of frequency f2 modulated by the operation of contact b of relay IR in accordance with the code is supplied over line YI-ZI to operate relay IJCR, and consequently to operate relay 0R of the office coding unit No. 2, these operations being carried out in theusual manner as already described in connection with the office coding unit No. l, until the laststep, comprising the return of the line circuits to normal is reached, at which time relays I5 and II-IGpick up and relays PC and PCP release. In vthe present case relays NR and TA now release successively to transmit a single brief impulse of frequency fl. over line YI-ZL energizing relay ICR to release relay IPC and thereby restore the polarity of the current in line Y2--Z;.I to normal. Relay L is reenergized upon the release of relay IPC, but this relay is vof the slow pick-up type and does not operate until after relay ICR has released at the end of the impulse, consequently relay ICR does not repeat this irn- Vpulse through the remote line unit to the remote` it will be evident that the control code will takev precedence unless relay GRis reversed lbefore relay @lvl has closed its front contact m and that.

the latter Vcase the indication code will take precedence because relay IBM will be unable to` pick up, because relay QR will have disconnected terminal B from wire Il in the pick-up circuit for relay iM. Otherwise the 4control code will take precedencaeven though relay IPC has been picked` up,vin which case the operation of relay ICR by the long `first step of the control code releases relay SPC immediately and holds the remote line circuit open to condition the stations to receive the controlcode, just as if relay IPC had not been operated. It will be clear that all of the features of the system by which interference is prevented as described in connection with the direct control of the stations function in the normal manner .when the carrier current control'is interposed.

Since the indication codes are used for reporting trains it is desirable to guard against their loss in transmission, due to temporary disturbances in the transmitting medium. In the systemof the Lewis patent this result is attained by registering -each element of the code bythe receiver at the transmitting station, and in releasing the starting relay only in response to the delivery to theline circuit of a complete code. It lfollows that a code which is interrupted due toa temporary cross or open in the line will stop the operation of the line relay at the transmitting station, and the code will be rra-initiated when the line. is restored. If the station does not sucoeed4 in completing its code after several attempts, a thermal relayCO is operated to temtransmitter to `allow other stations to transmit their codes. i I

It will be manifest from Fig. 2A that these provisions are leffective in both the direct control Y unit No. 3.

and the remote control forms of the system as disclosed herein insofar as the battery line circuit is concerned, since the operation of the station line relay R is dependent upon the integrity of the line circuit over which the station delivers its codes, but that on the other hand, the condition of the carrier current channel over which the indication codes are transmitted is not directly observable at the transmitting station.

However, the oice receiving apparatus functions in such a manner that if the delivery of an indication code is interrupted due to a temporary cross or open in the carrier current channel, the

resultant stopping of the periodic operation of the line relay R Will cause the transmission to be stopped and then 11e-initiated.

Upon the initiation of an indication code by a station on the remote line circuit, relay IPC is picked up by relay IR and relay PC by relay GR, along with the timing relays including relay' lLBP, and relay PC energizes relays NR and TA, While relay IPC energizes relay IPCP, which then releases relay L. Relay PC releases either upon the energization of relay -IB at the end of a complete code'or upon the release of relay `{lL-BP due to the stopping of the periodic operation of relay 0R before the code is completed, and upon releasing, releases relays NR and TA successively to transmit a single impulse of current of frequency ,fI over the line to pick up relay ICR and thereby release relay IPC as Yalready eX- plained. Relay IPC upon'releasing restores the polarity of the remote line to'normal, and if this occurs before the code is completed the periodic operation of relay Rat the transmitting station willeease because this relay is at the time responsive only toline current of Vreverse polarity, thereby releasing relay M to stop further transmission of the incomplete code, the apparatus then resetting to normal to initiate a new code in the usual manner.

It Will also be apparent that the carrier current system as herein disclosed issuitable for use over electrically long lines and that the carrier current units together with their receiving relays are adapted to be used Without change to serve as direct'repeaters for insertion at an intermediate point in such'lines when required. Thus, for example, a pair of C. C. units such as Nos'l and 3 may be located at such a point, C. C, unit No. 3 receiving modulated current of frequency fl to control a relay CR governing the transmission of control codes by C. C. unit No.1, and the latter unit receiving modulated current of frequency f2 to control another relay CR governing the transmission of indication codes in the opposite direction by C. C. The line circuits of the system of our invention are highly flexible in respect to their applicability to a wide variety of conditions likely to `be encountered in practice, and in different installations may vary widely in their arrangement. For example, it may be inconvenient to locate the control station at the junction of the two line sections as shown in Fig. 2B. -If this is the case, it may be located at any other point -on line Y2Z2, for example, at the distant end, with respect to the location ofthe central oiee, in which case the filter VF would be replaced by one adapted to pass the frequencies fI and f2 as well as voice frequencies. Furthermore, although the office coding unit No. `2V

controls a local dummy line this may as Well be an actual lineY circuit like -that controlled by Office .coding unit'No. l, to control one or more stations between the oliice and the location of the receiving relay IlCR, the remainder of the oice line unit being retained at the oilice, as shown. Alternatively, the office line unit may be located at the distant end of this line, in which case relay PR would be replaced by one responsive to either polarity and the unit would be connected across the distant end of the line through a suitable lter LF.

Although We have herein shown and described but two forms of apparatus embodying our invention and several modifications thereof, it will be understood that various changes and modifications may be made therein Within the scope of the appended claims Without departing from the spirit and scope of our invention.

Having thus described our invention, what We l claim is:

1. Ina remote control system, a remote line circuit extending from a control station through a plurality of remote stations, line wires providing a plurality of non-interfering communication l ter except when said stick relay is released, l

means preventing any code transmitter which has .been initiated from completing its code unless said stick relay is energized, a repeating relay at said control station adapted to deliver the codes received from said remote line circuit to one of said channels, means controlled by said repeating relay'in response, to the iirst impulse of a code received over said remote line circuit to operate said stick relay, a code receiver at the oice responsive to codes received over said one channel, .a rcode transmitter at the oflice adapted when initiated to deliver multiple impulse codes to another of said channels, a repeating relay at said control station adapted to deliver the codes received over said other channel to said remote line .circuit to control code responsive devices at the remote stations, means controlled by said oihce code receiver for delivering a single impulse to said another rchannel upon the reception of a predetermined number of impulses constituting 'a complete code over said one channel, means controlled by the repeating relay at the control station'in response to said single impulse for releasing said stick relay, and means preventing the delivery of said single impulse to said remote line circuit when said repeating relay responds to said impulse.

2. vIn Ya remote control system, a line circuit extending from a control station through a pluralityV of remote stations, line Wires extending from ysaid control station to a central oi'ce, a stick relay at said control station, a code transmitter at each remote station adapted when initiated to .deliver a multiple impulse co-de to said line circuit, means preventing the initiation of any code transmitter except when said stick relay is released, means preventing any code transmitter 'which has been initiated from transmitting its'code unless said stick relay is energized, a repeating relay at said control station adapted to repeat said codes .over said line Wires to the central oice, means controlled by said repeating relay in response to the rst impulse of a code to operate said stick relay, a code receiver at the oilice responsive to the codes repeated over` said vline-Wires, and means controlled bysad code receiver for Vreleasing said stick relay upon the reception of a predetermined number of impulses constituting a complete code. l

3.l In a remote control system, a line circuit extending from a control station through a plurality of remote stations, line wires extending from said control station to a central office, a code transmitter at each remote station adapted when .initiated to deliver a code to said line circuit, a repeating relay at the control station responsive to said codes, means including contacts of said repeating relay for delivering the codes to said line Wires, a code receiverv at the ofce responsive to the codes delivered to said line wires by said repeating relay, a stick relay at the con- .trol station, means for energizing said stick relay in response to the first operation of said repeating relay upon the initiation of a code yby any transmitter, means controlled bythe stick relay when energized for conditioning such trans mitter to complete its code, and means remotely Vcontrolled by the code Vreceiver at the offlce for releasing said stick relay uponv the reception of a complete code.

4; In a remote control system, a line circuit extending from a control station through a plurality of remote stations, line wires extending from said control station to a central ofce, a

stick relay at said control station, a code trans- Y tra adapted to repeat said codes over said line'wires A to the central oce, a line relay at the office responsive to the successive impulses of each code repeated over said line wires,and means effective in the event the` operation of said line relay Ais discontinued after it has responded to one or more impulses of a code for releasing said stic relay to re-initiate such code. s Y l 5,. In a remote control system, line VWires extending from a central oice to a distant control station, a line circuit extending from said Vcontrol station to a remote station, a code transmitter at said remote station adapted when initiated ,tov deliver a multiple impulse code to said line circuit, a repeating relay at said control station adapted to deliver said codes to said line wires, a line relay at the oflice responsive to the codes delivered to said line Wires by the repeating relay, and means remotely controlled by said line relay and effective if its operation is discontinued after it has responded to one or more impulses of a code for re-initiating the operation of said code transmitter.

6. In a remote control system, a line circuit extending from a control station through a plurality of remote stations, line Wires extending from said control station to a central oice, a code transmitter and a line relay for governing its operation at the oiiice and at each remote station, a repeating relay at said control station controllable from the oiice over said line Wires for delivering codes to said stations to which the station line relays are responsive, means controlled by said oflice code transmitter for operating the oflice line relay locally in accordance with a code and for simultaneously operating said repeating relay in accordance with such code.

and means including a repeating relay at the oflice controlled over said line wires by the station code transmitters for operating the oice `line relay in accordance with other codes.

. `tending from a central oflice to a control station, a line circuit extending from said control Y station to a remote station and including a source of direct current, a normally deenergized line relay of the two position stick polar type arranged 7. In a remote control system, line wires exto be held in its last operated position when ideenergized, a transformer at said control station interposed ,between the vrelay and said line vcircuit forcausingsaid relay to operateto reverse-and=to normal in response tofvar'iationsin `the current from saidsource, a code transmitter .atisaid remote kstation adapted to periodically vvary the current delivered to saidA linelcircuit to .operate theline relay inY accordance with a' code,

.means including contacts of the line-relay for .delivering said code to the 'line` Wires extending to the'ofce, a repeating relay at the oice rcoritrolled overi said 'line wires and repeating-'the operation of said line relay, and means controlled 'by said repeating lrelay for delivering an impulse over said line Wiresto restore said line relay to its normal position in the event it remains reversed for more than a predetermined time interval.

8. In a remote control'system, line Wires extending from a central 'olce to v'a controlv station and-affording two one Way communication channels, a line circuit-extending from said control station to a remote-station and including a source of direct current, a normally deenerigized line relay ofthe tWo position'stickpolar Arepeatingits operation, zand means controlledby y said repeating relay'for delivering "an impulse over; the other of saidf-channels'to-:restore said .line 4relay tolits normal positioniin"the event it remains reversedl for more'than'a lpredetermined time interval. f '-f V9. In a remote control system, 'lineiwiresfexl tending from a'central office to-'a distant control "station, a line circuitextending from the control jstation to a remotestation and normally supplied With direct current at said controlv station, a code transmitter at said remote station adapted when initiated to deliver. an impulse code to said line circuit but only if current of reverse polarity is being supplied thereto at said control station, means for initiating said transmitter to deliver the first impulse of such code effective only when current of normal polarity is being steadily supplied to said line circuit, a repeating relay at said control station responsive to said code, means including contacts of said repeating relay for delivering said code to said line wires, a line relay at the cnice responsive to codes delivered to said line wires by said repeating relay, means controlled by said repeating relay in response to the first impulse of a code for reversing the polarity of the current supplied to said line circuit, and means remotely controlled by the line relay and rendered effective when it has responded to the rst impulse of a code delivered by said repeating relay, for

restoring the polarity of theline circuit to norvmal upon the termination of such code.'

i 12. In a remote control system, two communif cation channels including the same line wires ar- 10. In a remote control' system, two` line wires extending from a control oice through a rst group of way stations to a control station, arst communication between the oflice and the sta-- tionsV of the second group, two sets of similar apparatus at saiclcontrol station each adapted to supply current' forcode transmission over one vof said superimposed channels and t'o amplify the 'current received 'from the oflice over the other, a changeoverr relay atsaid control station, means for' connecting one set' or the other of said apparatus to said channels, according tothe position of'said changeover relay, and means for transmitting codes over said first line circuit to effect the remote'control of 'said changeover relay from the oice and to indicate its position at' the oice.

11. In a remote control system, two line wires extending from a control oflice through a first group of way'stations to a control station, a first line circuit including said line wires and arranged to'pr'o'vide code communication between the ofllce and-f said stations, a second line circuit arranged to provide vcodeco'mmunication between said control station and `a second group of way stations, two'"alternating current channels superimposed upon said iirst line circuit and arranged for code transmission in opposite directions between the oilce and said control station and providingv comrnunicationY between the office and the stations of the' second group, two sets of similar apparatus 'at each end of said alternating'current channels eachlincluding anioscillator for supplying current Vto oneA channel and an amplier responsive to'currentA received over the other, a changeover relay at each end of'said alternating current channels, means forconnecting one'setV orithez'other'of said apparatustof said 'channels `at each end, 'according' to the position'of thev associated changeover relay, and means including manually operable levers atthe'oiice for operating said .changeover relays, 'such' operation being eiected when the changeoverfrelaycis at a point remote from the oice, by means of codes-transmitted oversaid line wires. f f l l ranged to provide code communication in opposite directions, each. having relayv contacts at one 'endV which control a receiving relay at the opposite end, a code transmitter and receiver located at a centralv ofiice having a transmitter relay and alinerIay of the stick polar type, a normally lclosed Kcircuit extending from said Yoiice to one -end Yof 'said channels including a source of direct current; contacts, of' said transmitter relay and the` primary of a. transformer, Asaid linev relay of the: stick pol'arzt'ype being connected to the secondary of saiditransformer, andthereby' rendered responsive fto current variations'in said circuit, a repeating relay in said' circuit :responsive to the operation jofv `said transmitterrelay contacts, means comprising saidv repeating relay for controlling the .contacts `in one' channel' to govern thexreceiving'rela-yat its distant'end, and means comprising the receiving vrelay of the other channel for varying the current inzthe circuit includ'- ing saidtransformer to-ithereby control ,said line relayi 'H 13. In a remote control system, two communication channelsl including` the same line wires-arrangedV to provide code. communication in oppo- -site directions, eachhaving relay contacts at one end'which control areceiving relay at the opposite end,;a code transmitter and receiver located at a distant station having a transmitter relay and a linerelay, a normally closed line circuit including said line relay andextending to a pointladja'cent *one end of said channels, said circuit also includingy a source of/ direct current, contacts of the .receiving relay ofv one channelv andthe primary of ka transformena relay of the'stick'polartype controllingf the contacts ofV saidother channel, and

`.having a windingconnected to the secondary of said transformer to render theY relay responsive to cu-rrent/variations-in said line circuit, a slow act- .ingv relay controlled by the receiving relay of said onechanneI, a-holding circuit for said stickpolar relay controlled by said slow acting relay' and Aeiective-.to preventr its response to variations in the current in saidline Vcircuit due tol the operation 'of-the receiving. relay of said one channel, and means comprising contactsofthe transmitter relay at theuclistant` station for varying the current in. said line relay.,f Y

, Y Y GEORGE W. BAUGHMAN.

NORMAN F. AGNEW.'

circuit to control said stick polar 

